Generally, a motor and fan are provided which draw fluid into a body; the fluid may be heated prior to exiting the body. The motor is susceptible to damage from foreign objects such as dirt or hair so conventionally a filter is provided at the fluid inlet to the blower. The fan and heater require power in order to function and this is provided via internal wiring from either a mains power cable or batteries attached to the appliance.
Conventional hairdryers have control buttons which can change one or more of the flow rate and the temperature of the fluid that exits the hairdryer. However, if the flow rate is increased there is usually a drop in the temperature of the fluid that exits the hairdryer that can be perceived by the user.
The temperature of the fluid that exits the hairdryer is also affected by other factors. There can be an electrical failure of some sort; alternatively dust and dirt can be pulled into the heater element and if this builds up it can burn and cause an increase in the temperature of the fluid exiting the hairdryer. Obviously, thermal protection is provided in the form of thermal cut outs such as thermal fuses or bi-metallic strips to prevent an excessive increase in temperature but such protection renders the hairdryer inoperable either temporarily or permanently.
It would be desirable to monitor the temperature and account for thermal fluctuations either due to a change in the flow rate or due to another factor. This provides a better user experience as changes in temperature when the flow rate is changed are minimised. Also, an increase in the temperature without a change in the set flow rate could be used to highlight a possible later problem and prevent the hairdryer becoming inoperable even if for only a short period of time.